I think some markets require that the drive doesn't provide power until it detects cadence.
CYC PHOTON
- Thread starter pxl666
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raylo32
100 kW
Even the TSDZ2 on OSF has a hybrid or power mode (I don't remember exactly what they called it) that simultaneously incorporates both torque and cadence inputs.
nervagon
10 kW
- Joined
- Nov 18, 2020
- Messages
- 576
So, a major event in ebike development just happened: ZF Centrix motor systems have been announced. I guess it is reasonable to ask "OK, how is this related to Photon?"
Well, the big deal is, this is appears to be an outrunner motor. From one of the biggest manufacturers of drive systems in the world.
I'd like to suggest that maybe, just maybe, CYC know what they are doing.
Not confirmed but mentioned in the video, is the casual comment that the motor is oil filled. If true I would speculate that might be to help with cooling.
What was shocking to me was the narrator describing being able to cook and render inoperable a motor from another manufacturer requiring dealer repair. CYC handle this sensibly, it is incomprehensible to me that not all manufacturers do.
*also of interest was DJI's entry into ebikes - but not using outrunner motors (which they will be very familiar with on their drones).
Well, the big deal is, this is appears to be an outrunner motor. From one of the biggest manufacturers of drive systems in the world.
I'd like to suggest that maybe, just maybe, CYC know what they are doing.
Not confirmed but mentioned in the video, is the casual comment that the motor is oil filled. If true I would speculate that might be to help with cooling.
What was shocking to me was the narrator describing being able to cook and render inoperable a motor from another manufacturer requiring dealer repair. CYC handle this sensibly, it is incomprehensible to me that not all manufacturers do.
*also of interest was DJI's entry into ebikes - but not using outrunner motors (which they will be very familiar with on their drones).
Gruesome
1 kW
Very odd that ZF, the german gearbox manufacturer, would not have protected the ZF trademark for all motor related things.
This is a subsidiary of that company. It's a ~€50B company. They make way more than transmissions for cars.
CentriX - Drive Unit
Get to know the ZF CentriX: The powerful and ultra-compact mid motor >
www.zf.com
The other question is, why now? Bosch got into this game quite a while ago.
Edit: - I'll add why (though "why now" still stands); ZF are probably looking at new areas to invest in, since their automotive base is going to reduce over the next few years. Fewer vehicles are going to be produced and EVs don't need such complex transmissions as ICE vehicles.
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Gruesome
1 kW
Oh really? Should be built like a tank then. 
(And hopefully won't go up in flames like the founder's Zeppelin.)
(And hopefully won't go up in flames like the founder's Zeppelin.)
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Yeah, I figure they'll know what they are doing. Though the same could have been said of Bosch. There seems to be some denigration of CYC's decision to use outrunners, in this forum; I reject that completely and feel somewhat vindicated by the fact that ZF think the same way as CYC. 90Nm of torque in a motor ~85mm diameter, including coaxial shaft and planetary gears.Oh really? Should be built like a tank then.
OTOH the motor is totally proprietary and locked down, you can't update the firmware or make adjustments.
Gruesome
1 kW
Well, outrunners make it harder to shed the stator heat. Just harder, not impossible. Maybe you just need to hire better engineers.
When I first installed the photon, I wondered why it uses a magnet for speed sensing, when there are a couple of alternatives - GPS built into the controller/display, or a sensor on the rear brake rotor.
GPS would make installation even easier and remove another external connection and cable, while at the same time adding potentially new capabilities for the app. And GPS is dirt cheap. The downside might be privacy and geo restrictions, which as a user I would not like but could be a real plus for regulators. Different markets could have their different speed limits enforced, for example.
Sensing the rear brake rotor would give much higher resolution for speed and distance, which has its own benefits. For example overrun could be more exactly controlled by distance instead of time.
GPS would make installation even easier and remove another external connection and cable, while at the same time adding potentially new capabilities for the app. And GPS is dirt cheap. The downside might be privacy and geo restrictions, which as a user I would not like but could be a real plus for regulators. Different markets could have their different speed limits enforced, for example.
Sensing the rear brake rotor would give much higher resolution for speed and distance, which has its own benefits. For example overrun could be more exactly controlled by distance instead of time.
raylo32
100 kW
I don't believe GPS is stable enough to use for instantaneous speed in a control function. Buildings, trees, etc. all create momentary dropouts where speed is not reported correctly. On my wooded C&O canal rides the GPS speed display on my Garmin is seldom correct.
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nervagon
10 kW
- Joined
- Nov 18, 2020
- Messages
- 576
95F degrees ride today on the new firmware. Thermal management seems to be improved. The spastic power output jumping all over the place is gone. Peak motor temperature for the ride was 82C. The Photon did quite well on the long climb at 95rpm cadence. It held between 700W-900W for most of the climb which was interrupted by a downshift by me near the end… resulting in less effort and a corresponding motor output drop to 500-ish watts.
Overall, the photon performed well today, and I would love to see detailed release notes on this firmware update. Voltage reading is fixed, and thermal management seems to be greatly improved.
Epithemeus
100 W
That is assuming that a rear brake rotor is present. "All bikes these days have disc brakes" is something I anticipate being a response. I definitely disagree though. I myself serve as a counter example and I know many others as well. Riding both new and old bikes.
In terms of other problems I could foresee would be are you attaching a magnet to the rotor? Sounds awkward. Using an optical sensor? Could work but is breaking new ground for ebike stuff whereas wheel speedometers are tried and true.
Probably not cheaper than a magnet and a switch. Even if it was there is also way more added complexity in the firmware that would quickly eat up cost difference in man hours developing and maintaining it.
Disagree. I'd say accuracy and interference would be the biggest issues. I go in a tunnel and I lose speed display? Tall buildings around? "But cellphones and stuff handle this just fine" is a potential counterpoint. Cell phones rely very heavily on tower triangulation to supplement and even then still struggle. The other option is to ramp up the complexity of the signal processing/software and ramp up the quality of the GPS hardware, again adding a ton of price. Maybe for some people who ride mainly in optimal conditions a cheap GPS chip would work just fine but it would be very far from a one size fits all reliable solution. I'd probably even say it's a one size fits a minority thing.
Sorry if I seem like I'm being super negative and slamming you down. That's not my intention, I do strongly disagree with your position, but I welcome it all the same
Mongo
1 kW
I've had the same so-so experience with GPS on wooded trails as @raylo32. I use it for course mapping, mostly out in the open, and to calibrate the motor system as best I can.
I think Shimano integrates a magnet driven speed sensor into their (probably Centerlock) brake disc rotor. I suspect there are several advantages in doing so - better protection and less or no wheel unbalancing come to mind. On IGH bikes with movable dropouts, consistent magnet/sensor alignment could be maintained.
Has anyone tried multiple magnets?
I think Shimano integrates a magnet driven speed sensor into their (probably Centerlock) brake disc rotor. I suspect there are several advantages in doing so - better protection and less or no wheel unbalancing come to mind. On IGH bikes with movable dropouts, consistent magnet/sensor alignment could be maintained.
Has anyone tried multiple magnets?
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Superb_Raccoon
100 mW
Depends on your final drive ratio.
In fact they recommend using multiple magnets for exactly that reason.
No. The rotor to output ratio is fixed.
The biggest advantage - for Shimano - is that owners have to replace with the same rotor, or the bike won't work. It does look a lot tidier, though.
I'm a fan of ~$10 rotors that are larger than originally fitted, and these work well.
The ability to sense field fluctuations at the rotor doesn't preclude also being able to sense a magnet on a spoke. The same sensor could do both.
I would imagine similar arguments could have been made about adding bluetooth. And yet, here we are.
Superb_Raccoon
100 mW
Hence FINAL, since you have to account for the bicycle's drive train ratios as well.
I can't tell if you don't understand or don't want to understand.
Gruesome
1 kW
Coming back to an old post, because I had nothing better to do and just counted the BikeOn teeth. The reduction ratio from motor to the red rotor is 11:144 (or 1:13.1), so at 9 mph the motor does 1464 rpm (24 turns per second) on a 700c wheel. That doesn't seem horribly slow, or does it?
Not really slow and that clearly suits your situation (and Aram's intended commuter market). Where I ride, is sometimes at significant power at 6-7kph, where the motor speed would be way slower. Typical situation would be in the video I posted a while back. How does the BikeOn ratio compare to other geared hub motors?
The speed range that my mid drive works at and produces decent output is well over 10:1, which is the major advantage of mid drives over hub motors. Not really needed for most commuting where you are more concerned about the behaviour at the higher end of the range.
BTW is there any conflict between your right heel and the motor casing (since you have such a small Q factor)? Or are your chainstays long enough to prevent that?
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Gruesome
1 kW
All good questions!
I don't know yet whether the BikeOn suits my intended application fully, since I haven't done the climbing test yet. Maybe I had mentioned it already, but one of my biking buddies was kind enough to look up the average power on his fancy (non-motorized) bike up Turnbull Canyon during our ride, and it was 110W. He was actually faster than me, so my 100W estimate was not far off. So the question is will the BikeOn be able to put out about 100W while going at 9-10 mph or 1500 motor rpm for a few miles without overheating? Because then I could climb that hill with 100+100W at twice my human-powered speed.
I do not know whether there is enough surface area to get rid of about 25W (assuming 80% motor & controller combined efficiency). The motor is only about 5cm tall and about 6cm diameter, so it has only about 160 cm^2 surface area. To get rid of 25W in still air with not more than say 50 Kelvin temperature difference you would need 25W/(50K*5W/(m^2*K)) = 0.1m^2 or 1000 cm^2 area. This assumes a heat transfer coefficient of 5 W/(m^2*K). Maybe the base plate adds another 100 cm^2. Then you are at say 250 cm^2 area available for convection cooling. You'd need to bring that heat transfer coefficient up by a factor 4, to 20 W/(m^2*K). Now, that is possible with enough air speed, but is 10 mph or 4.5 m/s enough for that?
Google says it might just work:
(picture from https://www.sciencedirect.com/topics/engineering/convection-heat-transfer-coefficient)
Reduction ratios in geared hubs: the G310 supposedly has 11:1 reduction gearing, so comparable.
Regarding heel clearance, the motor is very compact and well tucked away, but I have to be careful when routing the power cable up to the rear rack, so I don't keep hitting the big interference filter (?) that is part of the cable with my heel.
I don't know yet whether the BikeOn suits my intended application fully, since I haven't done the climbing test yet. Maybe I had mentioned it already, but one of my biking buddies was kind enough to look up the average power on his fancy (non-motorized) bike up Turnbull Canyon during our ride, and it was 110W. He was actually faster than me, so my 100W estimate was not far off. So the question is will the BikeOn be able to put out about 100W while going at 9-10 mph or 1500 motor rpm for a few miles without overheating? Because then I could climb that hill with 100+100W at twice my human-powered speed.
I do not know whether there is enough surface area to get rid of about 25W (assuming 80% motor & controller combined efficiency). The motor is only about 5cm tall and about 6cm diameter, so it has only about 160 cm^2 surface area. To get rid of 25W in still air with not more than say 50 Kelvin temperature difference you would need 25W/(50K*5W/(m^2*K)) = 0.1m^2 or 1000 cm^2 area. This assumes a heat transfer coefficient of 5 W/(m^2*K). Maybe the base plate adds another 100 cm^2. Then you are at say 250 cm^2 area available for convection cooling. You'd need to bring that heat transfer coefficient up by a factor 4, to 20 W/(m^2*K). Now, that is possible with enough air speed, but is 10 mph or 4.5 m/s enough for that?
Google says it might just work:
(picture from https://www.sciencedirect.com/topics/engineering/convection-heat-transfer-coefficient)
Reduction ratios in geared hubs: the G310 supposedly has 11:1 reduction gearing, so comparable.
Regarding heel clearance, the motor is very compact and well tucked away, but I have to be careful when routing the power cable up to the rear rack, so I don't keep hitting the big interference filter (?) that is part of the cable with my heel.
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80% would be a reasonable assumption for peak efficiency; at low speeds hub motor efficiency falls off a cliff and could be 50% or lower.
For an example, plug in a G310 into the motor simulator as a rough approximation for your system. It won't be accurate but gives a feel for how the parameters change.
